Endophytic Fungi from Frankincense Tree Improves Host Growth and Produces Extracellular Enzymes and Indole Acetic Acid

Abstract

Boswellia sacra, an economically important frankincense-producing tree found in the desert woodlands of Oman, is least known for its endophytic fungal diversity and the potential of these fungi to produce extracellular enzymes and auxins. We isolated various fungal endophytes belonging to Eurotiales (11.8%), Chaetomiaceae (17.6%), Incertae sadis (29.5%), Aureobasidiaceae (17.6%), Nectriaceae (5.9%) and Sporomiaceae (17.6%) from the phylloplane (leaf) and caulosphere (stem) of the tree. Endophytes were identified using genomic DNA extraction, PCR amplification and sequencing the internal transcribed spacer regions, whereas a detailed phylogenetic analysis of the same gene fragment was made with homologous sequences. The endophytic colonization rate was significantly higher in the leaf (5.33%) than the stem (0.262%). The Shannon-Weiner diversity index was H′ 0.8729, while Simpson index was higher in the leaf (0.583) than in the stem (0.416). Regarding the endophytic fungi’s potential for extracellular enzyme production, fluorogenic 4-methylumbelliferone standards and substrates were used to determine the presence of cellulases, phosphatases and glucosidases in the pure culture. Among fungal strains, Penicillum citrinum BSL17 showed significantly higher amounts of glucosidases (62.15±1.8 μM-1min-1mL) and cellulases (62.11±1.6 μM-1min-1mL), whereas Preussia sp. BSL10 showed significantly higher secretion of glucosidases (69.4±0.79 μM-1min-1mL) and phosphatases (3.46±0.31μM-1min-1mL) compared to other strains. Aureobasidium sp. BSS6 and Preussia sp. BSL10 showed significantly higher potential for indole acetic acid production (tryptophan-dependent and independent pathways). Preussia sp. BSL10 was applied to the host B. sacra tree saplings, which exhibited significant improvements in plant growth parameters and accumulation of photosynthetic pigments. The current study concluded that endophytic microbial resources producing extracellular enzymes and auxin could establish a unique niche for ecological adaptation during symbiosis with the host Frankincense tree.

Aspergillus terreus Inhibits Growth and Induces Morphological Abnormalities in Pythium aphanidermatum and Suppresses Pythium-Induced Damping-Off of Cucumber

“…In addition, El-Tarabily et al (2009) showed that the glucanase-producing actinomycetes could replace the use of metalaxyl in the control of Pythium aphanidermatum diseases. Many other fungi have the ability to produce extracellular enzymes such as Phoma medicaginis and Penicillium citrinum (Khan et al, 2016) and Talaromyces emersonii (McHale and Coughlan, 1981). The production of extracellular enzymes by Talaromyces flavus effectively contributed to control of Sclerotium rolfsii and Verticillium dahliae (Madi et al, 1997).…”

Transient leaf endophytes are the most active fungi in 1-year-old beech leaf litter

“…By contrast, the non-Clavicipitacean leaf-endophytes were rarely found to have beneficial effects for the host plant (Hyde and Soytong 2008;Rodriguez et al 2009;Khan et al 2016). While several saprotrophic fungi were recently shown to be capable of biotrophic interactions with host plants (Smith et al 2017), growing evidence suggests that some endophytic fungi become saprobes after leaf fall (Guo et al 2001(Guo et al , 2003Promputtha et al 2002Promputtha et al , 2005Promputtha et al , 2007Promputtha et al , 2010Shirouzu et al 2009;Suryanarayanan 2013;Saikkonen et al 2015;Szink et al 2016;Promputtha et al 2017).…”

The First Chloroplast Genome Sequence of Boswellia sacra, a Resin-Producing Plant in Oman

“…sacra is an endemic species growing only in Dhofar region of Oman [25–26]. The trees grow in desert-woodlands (Fig 1) with meager amounts of water and nutrient availability [27], whereas the domesticated trees are supplied with water [28]. In response to the incisions by the local people, the tree activates its defense mechanism by producing resin [28].…”

“…The trees grow in desert-woodlands (Fig 1) with meager amounts of water and nutrient availability [27], whereas the domesticated trees are supplied with water [28]. In response to the incisions by the local people, the tree activates its defense mechanism by producing resin [28]. The crystalline resin is used to create a fragrant smoke in homes and also sold in the market for income [26–27].…”